The present invention relates to an electrophotographic printer utilizing an electrostatic latent image developing means for forming an electrostatic latent image corresponding to information to be printed, on an image-bearing member, developing the electrostatic latent image with a magnetic developer containing magnetic toner, transferring the developed image to a recording medium, and heat-fixing the developed image to the recording medium, and more particularly to an improved thin electrophotographic printer which can be conveniently carried with hand.
In a conventional electrophotographic printer, an electrostatic latent image corresponding to a printer output (information to be printed) is generally formed on a cylindrical photosensitive drum, brought into contact with a magnetic brush of a magnetic developer conveyed on a developing roll containing a permanent magnet roll and disposed opposite the photosensitive drum, so that it is developed (visualized as a toner image). The developed image is then transferred onto a recording paper and heat-fixed.
The magnetic developer usable for a magnetic brush method as mentioned above is in many cases a two-component developer consisting of a magnetic carrier and a non-magnetic toner. However, in the case of using such a two-component developer, a concentration sensor and other members are required, failing to miniaturizing an electrophotographic printer satisfactorily. Accordingly, a one-component developer consisting of a magnetic toner, or a magnetic developer consisting of a magnetic toner and a magnetic carrier is mostly used for the electrophotographic printer.
With the above magnetic developer, the electrophotographic printer can be miniaturized to some extent, but there is a limit in the conventional electrophotographic printer. That is, since the conventional electrophotographic printer has a heat-fixing means comprising a heat roll containing a heat source and a pressure roll for pressing the recording paper to the heat roll, and since these rolls are provided with paper-separating fingers and other accessories, it is impossible to reduce the height of the roll pair of the heat-fixing means drastically. Accordingly, it has been impossible to make the conventional electrophotographic printer have an extremely reduced thickness.
Further, an increasingly higher demand is recently appreciated on a portable (hand-carrying) electrophotographic printer. Such a portable electrophotographic printer has already been commercialized for a type of using heat-sensitive papers. However, the information or image recorded on the heat-sensitive papers will disappear as the time goes. Accordingly, for the purpose of printing information which should be kept for a long period of time, the heat-sensitive paper type electrophotographic printer is not suitable.